Running at the full Vcc of 16V and the full frequency of 500kHz the 555 got
so hot I had to add a clip-on heatsink.

Tried slowing it down to about 140kHz and the heatsink still gets pretty
warm.

Is this normal?

Thanks.

"Ian Field" wrote in message
...
Running at the full Vcc of 16V and the full frequency of 500kHz the 555
got so hot I had to add a clip-on heatsink.

Tried slowing it down to about 140kHz and the heatsink still gets pretty
warm.

Is this normal?

Thanks.

I've run the NE555 at 12V and it barely got warm.

What load are you driving and what RC? Your dissipation could be coming from
the pin 7 sink discharging a large cap or sinking a high pull-up current.
Output drive doesn't fully saturate (iirc) so it is lossy when driving any
appreciable current.

"Oppie" wrote in message
...
"Ian Field" wrote in message
...
Running at the full Vcc of 16V and the full frequency of 500kHz the 555
got so hot I had to add a clip-on heatsink.

Tried slowing it down to about 140kHz and the heatsink still gets pretty
warm.

Is this normal?

Thanks.

I've run the NE555 at 12V and it barely got warm.

What load are you driving and what RC? Your dissipation could be coming
from the pin 7 sink discharging a large cap or sinking a high pull-up
current. Output drive doesn't fully saturate (iirc) so it is lossy when
driving any appreciable current.

Not using pin 7 at all - the RC is driven by pin 3.

I lowered the frequency still further - 8k2 & 3n3.

On Thu, 12 May 2011 17:55:33 +0100, "Ian Field"
wrote:

Running at the full Vcc of 16V and the full frequency of 500kHz the 555 got
so hot I had to add a clip-on heatsink.

Tried slowing it down to about 140kHz and the heatsink still gets pretty
warm.

Is this normal?

---
No.

Do you have pin 7 shorted to pin 8 or somehow connected to 16V?


--
JF

"John Fields" wrote in message
...
On Thu, 12 May 2011 17:55:33 +0100, "Ian Field"
wrote:

Running at the full Vcc of 16V and the full frequency of 500kHz the 555
got
so hot I had to add a clip-on heatsink.

Tried slowing it down to about 140kHz and the heatsink still gets pretty
warm.

Is this normal?

---
No.

Do you have pin 7 shorted to pin 8 or somehow connected to 16V?

Pin 7 was working just fine when I had it hooked up to a fast pullup
SB/emitter follower for driving MOSFETs, its not connected to anything now.

On Thu, 12 May 2011 17:55:33 +0100, "Ian Field"
wrote:

Running at the full Vcc of 16V and the full frequency of 500kHz the 555 got
so hot I had to add a clip-on heatsink.

Tried slowing it down to about 140kHz and the heatsink still gets pretty
warm.

Is this normal?

Thanks.


Post your schematic or a link to it.

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Obama is not the solution, Obama is the problem!

"Jim Thompson" wrote in
message ...
On Thu, 12 May 2011 17:55:33 +0100, "Ian Field"
wrote:

Running at the full Vcc of 16V and the full frequency of 500kHz the 555
got
so hot I had to add a clip-on heatsink.

Tried slowing it down to about 140kHz and the heatsink still gets pretty
warm.

Is this normal?

Thanks.


Post your schematic or a link to it.

I thought you killfiled me.

On Thu, 12 May 2011 19:20:42 +0100, "Ian Field"
wrote:


"Jim Thompson" wrote in
message ...
On Thu, 12 May 2011 17:55:33 +0100, "Ian Field"
wrote:

Running at the full Vcc of 16V and the full frequency of 500kHz the 555
got
so hot I had to add a clip-on heatsink.

Tried slowing it down to about 140kHz and the heatsink still gets pretty
warm.

Is this normal?

Thanks.


Post your schematic or a link to it.

I thought you killfiled me.


That gets automagically withdrawn when a technical question is asked
;-)

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Obama is not the solution, Obama is the problem!

Ian Field wrote:
Running at the full Vcc of 16V and the full frequency of 500kHz the 555 got
so hot I had to add a clip-on heatsink.

Tried slowing it down to about 140kHz and the heatsink still gets pretty
warm.

Is this normal?

Thanks.


Try again at a somewhat lower voltage, you may have exceeded
vcc for this particular unit and/or caused latching somewhere,
in which case almost the black magic smoke comes out.

"Sjouke Burry" wrote in message
...
Ian Field wrote:
Running at the full Vcc of 16V and the full frequency of 500kHz the 555
got so hot I had to add a clip-on heatsink.

Tried slowing it down to about 140kHz and the heatsink still gets pretty
warm.

Is this normal?

Thanks.
Try again at a somewhat lower voltage, you may have exceeded
vcc for this particular unit and/or caused latching somewhere,
in which case almost the black magic smoke comes out.


Almost every datasheet I've seen says 16V - ISTR the Hitachi DS says 18V.

On Thu, 12 May 2011 19:48:06 +0100, "Ian Field"
wrote:


"Sjouke Burry" wrote in message
...
Ian Field wrote:
Running at the full Vcc of 16V and the full frequency of 500kHz the 555
got so hot I had to add a clip-on heatsink.

Tried slowing it down to about 140kHz and the heatsink still gets pretty
warm.

Is this normal?

Thanks.
Try again at a somewhat lower voltage, you may have exceeded
vcc for this particular unit and/or caused latching somewhere,
in which case almost the black magic smoke comes out.


Almost every datasheet I've seen says 16V - ISTR the Hitachi DS says 18V.


Perhaps a large capacitive load?

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Obama is not the solution, Obama is the problem!

"Jim Thompson" wrote in
message ...
On Thu, 12 May 2011 19:48:06 +0100, "Ian Field"
wrote:


"Sjouke Burry" wrote in message
...
Ian Field wrote:
Running at the full Vcc of 16V and the full frequency of 500kHz the 555
got so hot I had to add a clip-on heatsink.

Tried slowing it down to about 140kHz and the heatsink still gets
pretty
warm.

Is this normal?

Thanks.
Try again at a somewhat lower voltage, you may have exceeded
vcc for this particular unit and/or caused latching somewhere,
in which case almost the black magic smoke comes out.


Almost every datasheet I've seen says 16V - ISTR the Hitachi DS says 18V.


Perhaps a large capacitive load?


Been bench testing with no load (apart from driving the CR) and then with a
BC327/337 complementary emitter follower pair.

On Thu, 12 May 2011 20:38:39 +0100, "Ian Field"
wrote:


"Jim Thompson" wrote in
message ...
On Thu, 12 May 2011 19:48:06 +0100, "Ian Field"
wrote:


"Sjouke Burry" wrote in message
...
Ian Field wrote:
Running at the full Vcc of 16V and the full frequency of 500kHz the 555
got so hot I had to add a clip-on heatsink.

Tried slowing it down to about 140kHz and the heatsink still gets
pretty
warm.

Is this normal?

Thanks.
Try again at a somewhat lower voltage, you may have exceeded
vcc for this particular unit and/or caused latching somewhere,
in which case almost the black magic smoke comes out.


Almost every datasheet I've seen says 16V - ISTR the Hitachi DS says 18V.


Perhaps a large capacitive load?


Been bench testing with no load (apart from driving the CR) and then with a
BC327/337 complementary emitter follower pair.


Post your schematic or a link.

...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Obama is not the solution, Obama is the problem!